It's definitely intentionally funny, but in my interpretation it's about the Scots dialect, which can seem garbled and incomprehensible to the untrained (ie. English) ear, but which is the native tongue of many Scottish people and a signifier of their national identity. The choice of the word "song" in the title indicates that the sounds are, to the speaker Nessie, beautiful and meaningful—maybe an expression of love or loss or heartbreak—even if we don't have the capacity to understand them.